U.S. Pat. No. 5,129,570, hereby incorporated by reference, discloses a surgical stapler configured for applying rows of staples in lieu of suturing tissue. This type of surgical device greatly facilitates surgical procedures, and desirably reduces the time otherwise required for suturing tissue.
The surgical stapler disclosed in the above-referenced patent is configured to employ a removable staple cartridge, which typically includes a plurality of rows of staples. Attendant to each use of the surgical stapler, a fresh, unused staple cartridge is inserted into a frame of the stapler, with the device then positioned for use for suturing tissue. The stapler includes one or more firing wedges which can be advanced through the staple cartridge, and which cooperate in a cam-like manner with drivers within the cartridge to fire the staples, driving them through tissue and against an associated anvil of the stapler for closing the staples. For reuse, the firing wedges are retracted, the used staple cartridge removed, and an unused staple cartridge inserted into the device.
While some staplers are configured to perform the sole function of stapling, one particularly useful configuration of a surgical stapler effects simultaneous cutting and stapling (i.e., suturing) of tissue. Such devices, sometimes referred to as linear cutters, include a knife blade which is advanced together with the firing wedges of the surgical stapler during use. In this manner, cutting of tissue is effected simultaneously with stapling, greatly facilitating efficiency in surgical procedures.
In order to preclude inadvertent use of a stapler with a used staple cartridge, thereby avoiding inadvertent cutting of tissue without simultaneous application of staples, surgical staplers are ordinarily provided with locking mechanisms which prevent actuation of the device unless fitted with a fresh, unused staple cartridge. U.S. Pat. No. Re. 34,519, to Fox et al., hereby incorporated by reference, discloses various embodiments of such locking mechanisms, with the above-referenced U.S. Pat. No. 5,129,570 disclosing further embodiments of such locking mechanisms.
In the locking mechanisms disclosed in U.S. Pat. No. 5,129,570, the knife blade of the illustrated surgical stapler is configured to cooperate with a member provided on an unused staple cartridge for permitting advancement of the knife blade, and actuation of the stapler, when fitted with the unused cartridge. In particular, the knife blade is mounted for limited vertical movement in opposition to a biasing spring, which spring ordinarily urges the knife blade into a locked position in association with a roof member of the stapler. Insertion of an unused staple cartridge into the device acts to displace the knife blade, in opposition to the biasing spring, into alignment with a slot defined by the roof member. This permits advancement of the knife blade and the associated firing wedges of the stapler, thus permitting simultaneous cutting and stapling of tissue. During advancement of the knife blade, the cooperating member on the staple cartridge is displaced. As a consequence, upon retraction of the knife blade and firing wedges, the knife blade is urged by the biasing spring into engagement with the roof member and out of alignment with the slot therein, thus preventing reuse of the device until fitted with an unused staple cartridge.
In particular, current commercial embodiments of surgical staplers in accordance with the above-referenced patent include a rotatable member mounted on the staple cartridge for cooperation with the associated knife blade. This rotatable member (sometimes referred to as a swing tab) is configured to interferringly engage the body of the staple cartridge as the member is rotated by the knife blade, thus providing a snap-over like action to maintain the rotatable member in an out-of-the-way disposition. This prevents the knife blade from engaging the rotatable member and returning to its original position as the blade is retracted.
In U.S. application Ser. No. 08/611,161 filed Mar. 5, 1996 by the same inventor as the present application, a surgical stapler includes a staple cartridge having a rotatable member which is initially positioned to coact with a knife blade of the surgical stapler to position the knife blade for distal movement in the device, thus permitting actuation for simultaneous cutting and stapling of tissue. Notably, the rotatable member is specifically configured to move to an out-of-the-way position during actuation of the device without application of undue force to the rotatable member. Convenient and efficient use is facilitated by the resultant reduction in "force to fire" of the stapler.
The surgical stapler disclosed in the aforementioned application includes a frame, and a staple cartridge positionable in the frame. The staple cartridge comprises a cartridge body containing at least one row of staples, with the cartridge defining an elongated knife slot. At least one firing wedge is carried by the frame of the surgical stapler for movement longitudinally of the stapler. Such longitudinal movement, distally of the stapler, effects sequential driving of the staples from the staple cartridge through tissue and against an associated anvil of the stapler.
A knife blade travels across a spacer which is mounted into the frame of the stapler for movement through the elongated knife slot defined by the staple cartridge. The knife blade is also vertically movable between a first, locked position wherein the knife blade is substantially prevented from moving through the knife slot, and a second, unlocked position wherein the knife blade is movable through the slot in the staple cartridge.
The staple cartridge includes a rotatable member which is movable from a first position to a second position. In its first position, the rotatable member is engagable with the knife blade as the staple cartridge is positioned in the frame of the stapler. This engagement acts to move the knife blade from its first, locked position to its second, unlocked position.
During actuation of the stapler, the rotatable member on the cartridge is moved to the second position thereof by the knife blade as the knife blade is advanced in forward or distal direction through the knife slot. Simultaneous cutting and stapling of tissue is effected during distal advancement of the knife blade.
The rotatable member on the staple cartridge includes a resiliently flexible portion which is yieldably engagable with the body of the staple cartridge as the rotatable member is moved from its first position to its second position. After such movement, the flexible portion on the rotatable member is engagable with the cartridge body to maintain the rotatable member in the second position thereof. Upon retraction of the knife blade, the blade returns to its first, locked position wherein it is substantially prevented from movement through the knife slot (i.e., its position prior to insertion of an unused staple cartridge). This takes place since the rotatable member on the staple cartridge has been moved to its second position, and thus is no longer engagable with the knife blade. Reuse of the stapler is effected by removal of the spent cartridge, and insertion of a fresh, unused staple-filled cartridge.
A first end portion of the rotatable member is pivotally mounted on the cartridge body of the staple cartridge. The resiliently flexible portion of the member comprises a cantilevered arm at this first end portion, which arm is engagable with the cartridge body as the rotatable member is moved from its first to its second position. Additionally, the rotatable member includes a cam projection engagable by the knife blade of the stapler as the knife blade is advanced distally through the knife slot. The cam projection facilitates movement of the rotatable member to the second position thereof. The cam projection is provided generally at a second end portion of the rotatable member, spaced from the first end portion thereof.
The device described provides an effective arrangement for preventing inadvertent use of the surgical stapler with a used staple cartridge. It is, however, possible that a build up or accumulation of tissue around the locking mechanism could inhibit the knife blade from efficiently seating against the roof member in the retracted condition.
Additionally, the retraction of the knife during multiple return strokes may cause a portion of the knife blade to embed into the roof member of the locking mechanism. This embedding, plus the tissue buildup can possibly cause an occasional inhibition of the knife to be efficiently restored to its full upright position, locked behind the roof member.